Damper mechanisms are used to damp torsional vibration in the power transmission systems of vehicles. A clutch device that transmits and shuts off torque to and from an engine will be described here as an example.
A clutch device is made up of a clutch disk assembly that is disposed near a flywheel, and a clutch cover assembly for pressing the clutch disk assembly against the flywheel. The clutch disk assembly functions both as a clutch and as a damper.
The clutch cover assembly has an annular clutch cover that is fixed to the flywheel, a pressure plate provided so as to be capable of moving in the axial direction and rotating integrally with respect to the clutch cover, and a diaphragm spring that biases the pressure plate toward the flywheel.
The clutch disk assembly is made up of a clutch disk that is sandwiched between the pressure plate and the flywheel, a pair of input plates disposed opposite each other and to which the clutch disk is fixed, a hub flange disposed in the axial direction between the pair of input plates, coil springs that elastically link the pair of input plates and the hub flange in the rotational direction, and an output hub that is elastically linked in the rotational direction with respect to the hub flange. The pair of input plates, the hub flange, and the coil springs constitute a damper mechanism.
With a conventional clutch disk assembly, a stop pin is used to restrict relative rotation between the hub flange and the input plates within a specific range of torsional angle. This stop pin links the pair of input plates and passes through a hole formed in the hub flange. A stopper mechanism is realized when the stop pin hits the hole in the rotational direction.
However, the stop pin needs to have a consistent diameter in order to ensure strength, and must be disposed more to the inside in the radial direction than the outer peripheral edges of the pair of input plates. In this case, an adequate relative torsional angle is not obtained even when coil springs with high stiffness are used. Therefore, with a conventional stop pin type of stopper mechanism, the performance of the coil springs cannot be utilized to full advantage.
In view of this, a damper mechanism has been proposed which employs a stopper mechanism in which no stop pin is used (see Japanese Laid-Open Patent Application H9-196078, for example).